The Cross River gorillas (Gorilla gorilla diehli) at Mawambi Hills, South-West Cameroon: habitat suitability and vulnerability to anthropogenic disturbance.

ABSTRACT

Only about 300 individuals of the Cross River gorilla (CRG; Gorilla gorilla diehli) survive today. The subspecies is endemic to approximately 12-14 sites at the Cameroon-Nigeria border, and is critically endangered. To understand survival prospects of the CRG at Mawambi Hills, Cameroon, a maximum entropy (MaxEnt) distribution model was used to predict the distribution of gorillas. Overall, 24% of the study area was predicted to be suitable for gorillas. The most important predictors of gorilla distribution were elevation as a surrogate for accessibility (52.4%), distance to nearby villages which represents proximity to anthropogenic disturbance (22.7%), and slope steepness as a proxy for security (19.4%). Gorillas mainly occupied slopes of steep hills and avoided areas of human disturbance. To evaluate the spatial relationship between gorilla distribution and human activities, the predicted habitat suitability map was overlaid with a kernel density map of human activities. A positive correlation was found between locations of human activity and suitable habitat for gorillas (r = 0.5). This suggests that anthropogenic pressures in previously unused forest areas are increasing as a result of resource depletion at lower altitudes, consequently putting the gorillas at greater risk. Conservation management plans that seek to reduce human encroachment into habitats preferred by gorillas such as steep hills will probably contribute to gorilla survival.